An image display device is known that displays an image in a stereoscopic fashion. For example, patent document 1 discloses an image display device which includes a plurality of transparent fibers arranged in a two-dimensional matrix pattern, the length of each fiber being changed at the display end for each individual pixel which is the smallest unit forming a display screen, and light sources arranged uniformly behind the respective fibers. This image display device provides a sense of depth to the displayed image by changing the length of each fiber in a stepwise manner at the display end and thereby creating relative differences in height at the top ends of the respective fibers.
A three-dimensional display device for displaying a stereoscopic image, called a volumetric display, is also known (for example, refer to patent document 2). The volumetric display scans laser light from a light source by using a MEMS (Micro Electro Mechanical System) mirror, for example, so as to display images of cross sections of an object onto virtual screens stacked in multiple layers, and produces a stereoscopic image by combining the plurality of images. Among others, a retinal scanning volumetric display is known that projects a stereoscopic image directly into the human eye by scanning a plurality of laser lights of different focusing distances over the retina (for example, refer to non-patent document 1).
FIGS. 16A and 16B are diagrams for explaining the basic principle of the retinal scanning volumetric display. A plurality of laser lights from a plurality of optical fibers 101 respectively connected to a plurality of laser light sources are projected so that the respective laser lights are focused at different positions in the horizontal direction (depth direction) as indicated, for example, by black dots in the figures. In FIGS. 16A and 16B, the four laser lights projected from the optical fibers 101 into a viewer's eye 105 via projection lens 102, 103, and 104 are indicated by solid and dashed lines.
The plurality of laser lights are superimposed one on top of another to form a multifocal beam, which is scanned over the viewer's eye 105 by a scanner 106 to form a stereoscopic image with a plurality of images stacked in layers. For example, when a viewer adjusts his/her crystalline lens so as to bring point A onto the retina, as shown in FIG. 16A, the viewer has the sensation that the lens is focused on a distant object.
On the other hand, when the viewer adjusts his/her crystalline lens so as to bring point B onto the retina, as shown in FIG. 16B, the viewer has the sensation that the lens is focused on a near object. In this way, the viewer can perceive the depth when viewing the image presented by the volumetric display.
An array of a large number of fiber pigtail modules is used as the laser light source for the volumetric display. This, however, increases the overall size of the device; therefore, it is preferable to use an arrayed optical module as the laser light source in order to reduce the size of the device.
In non-patent document 1, it is described that an array of optical fibers respectively connected to a plurality of LD (laser diode) devices is used as the laser light source for the volumetric display. In the volumetric display of non-patent document 1, each optical fiber in the array is connected at one end to a corresponding one of the LD devices and cut at an angle at the other end, and the position in the depth direction of the image to be projected is controlled by varying the distance from the exit end face of each fiber to the retina.